Single axle or tandem trailer?

[slowmover]

Originally Posted by Hersbird

I don't think anybody has answered the question. Not is 1 or 2 axles better for towing, but does 2 axles and 4 tires have say twice the rolling resistance of 1 axle and 2 tires? I wouldn't think twice as much as they will be carrying 1/2 the load and can be done with lower mass axles, wheels, and tires compared to a single heavy duty axle, wheels, and tires. It will be more though but any of this is small compared to potential aero drag of what you put on the trailer, or the huge hit you get crawling around off road even without a trailer.

RR doesn’t mean much with trailers. It’s the aero penalty. Unlike a car with work commute and shopping, an RV spends little engine time off highway. Generally.

The tracking stability of Tandem means fewer steering corrections. Etc. It’s just easiercin every situation. ESPECIALLY backing.

[slowmover]

Originally Posted by spazatac

Yes. I used to have a 7000# featherlite toyhauler with all the amenities I towed with a cummins van and got 15 mpg average. It was sweet and I regret selling both, but it was to big to pull where I want to go and I need 4x4.



I talked to a couple who drove the Yukon trail pulling a bigfoot fiberglass camper. They bent both axles, so I don't want to screw around.

I'm guessing the new 7x16 toyhauler dry will weigh around 3k. Then loaded down with a finished interior, a couple motorcycles and tools and as much glamping gear I can cram in there. Then 100 gallon shower water tank which wont be full, usually.. A 20 gallon drinking water tank. All that crap might weigh 5k so I'm up to 8k or about 75% of capacity which might ride rough.. Hence de-leafing, but this is all speculation. Weight might add up quicker than I think. Maybe it will ride great as is, but I'm thinking I want longer leaf springs if using a single axle, or something to help the ride..



Exactly.. But the offset of truck rims, mine being 17", is a little more than the centered trailer rims I think so the tires would be to close to the wheel wells or rub. Plus the truck center hole is smaller than the trailer rim center hole. Two hurdles.. And are trailer studs 9/16"? Walter at Jensen trailers said he would use wheels I supply but I haven't figured out how, or how large to enlarge the center hole.



I'll use a straight axle. But using trailing arms/panhard bar with airbags or longer leafs would be nice.

Blowing a tire is definitely a concern. Especially since this is a narrow track trailer, meaning no fenders, and the wheels are under it in wheel wells. So, a 7' wide trailer that's over 8' tall? Yeah, I think you just convinced me to use tandem axles. But that limits what type of suspension I use to the stock 2' leaf springs.

The "gap" between the TV and Trailer is responsible for about 25% of the drag of the combo. Possibly this is the area that would yield the most mileage gain. Also no surprise, this would be the most complicated because of the articulation and clearance.

Torsion axles. Period.

And disc brakes.

100-gal Water way way way too much. Maybe 45. Too much weight when full either moving or stationary.

Suggest you spend more time looking at what’s out there retail. Don’t get far away in design. Stay very close. Trailer engineering is serious business.

.

[Daschicken]

8K+ is a hell of a lot of weight for two tires. Even the 235/85/R16 trailer tires my workplace sells wouldn’t be enough to carry that weight at 110 PSI. Those things have sidewalls at least an inch thick too. Whatever you get, bring a temperature gun and make sure the tires aren’t getting above 180F. Preferably lower.

[spazatac]

Originally Posted by Daschicken

8K+ is a hell of a lot of weight for two tires. Even the 235/85/R16 trailer tires my workplace sells wouldn’t be enough to carry that weight at 110 PSI. Those things have sidewalls at least an inch thick too. Whatever you get, bring a temperature gun and make sure the tires aren’t getting above 180F. Preferably lower.

Yes and good thing I started adding worst case scenario weights. I doubt it would ever weigh 8k and I was thinking 9k axle, but didn't think tires..

Two axles will be installed..

[freebeard]

I came here to say what slowmover would say but he already did.

As for the question, I'd assume that rolling resistance is related to weight over contact area. [?] Four tall, narrow tires would have less frontal area for drag.

[spazatac]

Originally Posted by freebeard

I came here to say what slowmover would say but he already did.

As for the question, I'd assume that rolling resistance is related to weight over contact area. [?] Four tall, narrow tires would have less frontal area for drag.

Thanks.

Since I started this thread I was told first hand about how offset truck rims did actually ruin the bearings on a trailer, so Ive decided (subject to change lol) to run 16" centered trailer rims on the trailer, but be able to use the trailer spare for the truck if needed by using a tire that's within a tenth of a inch outside diameter of my 17" truck tires. The other choice would be to buy new 16" rims for the truck so I could run the exact same eight tires all around.

And two axles are definitely needed just for safety mainly. And I have to have 100 gallons of water for my long haired GF to join me. Actually two 50 gallon tanks, which don't need to be completely filled, but available if needed.

If torsion axles are so great, why do the serious off roader's pulling trailers choose leaf springs? My take is repairs are possible unlike torsions, which would need complete replacement. Limping back for repairs is possible by cramming a log between the axle and frame for example.
Also, one off road trailer company tried torsion axles for a while and found the rubber wears out prematurely because of dirt getting in there. Torsion's don't last as long. Estimates range from 10-15 years highway use. I'm guessing allot less offroad. I'm on the fence but leaning towards the leaf springs.

[skyking]

Great discussion
I have a much lighter trailer design in mind, and I am going so far as to design the wheel well area to accommodate either a pair of small 2200 pound axles or a single 5200.
My concern is the inherent bouncyness of ride with a single large tire/axle. I think a torsion with supplemental shock absorber will be a must with a big single. I have had torsions and the ride is great, but they were always tandems.
conventional spring single axles always 'launch' more than a set of tandems. More like a basketball
It is even more problematic when you try to cover a wide range of weight, as you are proposing. When light, even airing down the tires won't compensate for the stiffness of lightly loaded springs.

[freebeard]

If torsion axles are so great, why do the serious off roader's pulling trailers choose leaf springs?

I'd guess the geometry. A single trailing arm holds the wheel parallel to the body. A leaf spring holds them perpendicular to the surface (whatever that might be doing).

I designed a teardrop trailer with 4 10-12" wheels on two-wheel bogies on single pivots on a rigid cross-member.

Here's an aerodynamic study:

http://xinzhang.ust.hk/research_proj...roject13_1.png

[skyking]

If torsion axles are so great, why do the serious off roader's pulling trailers choose leaf springs?

It relates to tandem axles, and how a torsion axle pair does not equalize over rough terrain and approach angles.
A well -lubricated set of equalizing spring hangars does a great job of trying to keep an equal weight on both tires.
Torsion axles do nothing at all. In fact, you can put an 8" tapered block in front of either axle, drive up on it, and the other tire will come off the ground and you can change it without a jack!
So in a truly lumpy environment, the conventional springs will keep a better even pressure on the ground in trying offroad conditions.
Single axle, the problem is moot.

Tandem torsions rule the pavement, if set up flat.

[slowmover]

The best survey of type is Australia.

The WORST POSSIBLE leaf arrangement is what is seen in US. Fundamentally unstable.

Leafs are cheap. That’s the reason used.

Torsion outlasts it. Leafs need rebuild almost continually. Someone says they don’t, tell them to disassemble. The wear is always there. Dozens of wearing parts per wheel. A Tosiin AXLE has about seven all told.

Slow miles offroad DONT trump miles at highway speed.